1. Field of the Invention
The present invention relates to a warning device for warning a filter-changing time, which is suitably used for a vehicle air conditioner, for example.
2. Description of Related Art
Because dust and smelling components are physically collected into a filter for an air conditioner, the filter is clogged with using time and using condition, and an air amount passing through the filter is decreased. For preventing a decrease of air-conditioning capacity due to the clogging of the filter, for example, in a conventional vehicle air conditioner described in JP-A-7-81392, an air amount passing through a filter is estimated based on a rotation speed of a blower fan and a vehicle speed, and a filter-changing time is determined so that a warning signal is output.
However, generally, the air amount passing through the filter is changed in accordance with a clogging degree of the filter. Therefore, it is difficult to accurately determine the air amount passing through the filter by the estimate due to the rotation speed of the blower fan and the vehicle speed. Further, the clogging degree of the filter is greatly relative to the using condition of the filter. Here, a sensor for detecting a signal directly relating to the air amount passing through the filter or a sensor for detecting a contaminated degree of air sucked into the filter may be provided so that the filter-changing time is accurately determined. However, in this case, production cost is increased with the sensor arrangement.